In this study
we were interested in the influence of laser power and stimulation frequency
on the optogenetically induced BOLD signal of the hippocampal network in
mice. We induced expression of channelrhodopsin-2 in
Ca2+/calmodulin-dependent protein kinase II-expressing neurons by virus
injection. Laser stimulation was periodically applied through an optical
fiber in the left hippocampus with block and event related designs using
different power and stimulation characteristics. We found activation and deactivation
due to laser heating effects even at low power levels and diverse activation
patterns in dependency of stimulation length and frequency